if the side panels are dimensioned in multiples of 32mm then the stops work from either end of the 32mm holey rail.  You can use non-32mm dimensions, however you must always register the rail to either the top   
only, or the bottom only of the panel.  Just mark the chosen reference side accordingly and pay close and constant attention to registering the rails against the reference edge.  This is not a concern when building side panels in multiples of 32 mm as registration will be inherently correct by design.

Likewise, if you are using the LR 32 to place Euro cup hinges on corresponding doors, the same method applies.....If 32mm multiples then both ends work, if not 32mm multiples, then always reference either top or bottom only for rail registration.

And if I have a cabinet that is longer than my holy rail?

Then make your cabinet shorter   Just kidding....you could still use the rail from both ends, however there would be a discontinuity of the 32mm hole spacing at one point.

If you were drilling holes along an 80" cabinet for example, would you need a full set of 32mm spaced holes for the entire height?  If not then it would still be possible to reference from both ends understanding that at some point, there will not be a 32mm space between two holes somewhere.

I didn't want to constantly have to overthink my cabinets and adopted the 32mm multiples.  Life got simpler after that